He told the story Monday night while appearing onThe Tonight Show With Jimmy Fallon.

Apparently he had a weed lollipop the night before the Young Hollywood Awards, where he was presenting an award. And that's when he got a NARB (a non-apparent reason boner), and had to subtly cover his junk on the red carpet.

That's embarrassing, but we're pretty sure there are worse moments to get a surprise erection.